Hello there, I'm kinda confused by the whole tantrum my phone is throwing since yesterday morning because it looks like a software error to me but seems to have been caused by having dropped it. 

The Phone was charged (think like 70%) when i dropped it, and showed the "no battery" graphic that comes up when you try booting it on a dead battery as i looked at it after the fall. Then i connected the charger thinking the battery being dead was odd and since then it's deader then i've ever of heard phones being. 

Currently the phone automatically tries booting as soon as it's connected to power, but does not react to any input or input combination whenever not connected to power. Also it doesn't boot successfully, which is part of why I'm so stumped, since it's caught in a bootloop as long as it has external power and dies as soon as disconnected. Holding the Power button when connected to power does nothing, it does however say "Fastboot" upon holding power+vol.down and then gets stuck there unless you keep holding the power button or disconeect it from power. Also I'm unable to get into the recovery menu by holding power+vol.up, just does nothing no matter what as far as i can tell. 

This morning i tore the backplate off it since i thought this issue may be caused by disconnected or loose battery cables, and the back needed replacing anyway, but after reseating them i've still gotten nowhere. I did meassure what I think were the battery terminals of the battery on both cables, the larger pads anyway, and got around 4.15V for the left one and a little above 4.3V for the right one. I also cleaned the main frame using isopropyl and Qtips before reassembling and all buttons feel "right", so i'm also rather sure that no button is stuck and causing this.  An older colleague of mine also suggested throwing it in the freezer (was my first time hearing that too lol) and trying to boot it, which appearently helped him before, but didn't work for me sadly. 

Thx in advance to anyone giving advice or "inspiration" on what else to try. My next idea would be trying some diagnostic software like my father did with my galaxy ace and samsung keys back in the day, but i don't know the name of the according software yet, my laptop appearently doesn't actually recognize the phone and I'm done for today since it's late and i really need to do other important stuff. 

Xiaomi Redmi Note 12 Pro+ Bootloops since dropped.